This invention relates to crimping apparatus and more particularly relates to a tool of this type for crimping a connector sleeve to a stranded cable.
Generally, a crimping tool must be capable of exerting sufficient pressure on several surfaces of a connector sleeve to cause the sleeve walls to be deformed so as to engage and frictionally hold the stripped portion of a cable which has been positioned within the sleeve bore. A crimping tool must not exert pressures in excess of this captivating pressure, since overpressurization often results in both cable strand breakage and connector sleeve splitting, which render the crimped connector useless for its intended purpose.
The crimping tool may also be required to perform other functions ancillary to the crimping process. These functions may include the forming of mounting or bearing surfaces on the sleeve, the forming of the entire connector into a shape as required by mounting volume considerations, the forming of apertures for the passage of mounting hardware through the sleeve or the sleeve and cable, the preventing of the application of excessive force in order to minimize distortion of a pre-formed sleeve portion or surface or the maintaining of a particular shaped surface or section while pressure is applied to adjacent surfaces or sections.
The crimping tool may, additionally, be required to establish and hold the connector sleeve and cable in a rigid relationship to one another and to the crimping tool. This positioning apparatus complicates the crimping tool and a preferred tool should be operable without elements utilized solely for holding the connector sleeve and the cable.
Crimp-type connectors have been formed with a flat portion having a through aperture, to allow passage of mounting hardware, and a tube, with its axis displaced above the plane of the flat portion, into which a cable end is placed. This offset tube is then crimped to the cable end by a tool which applies opposed forces of a magnitude sufficient to press the inner wall of the tube into intimate engagement with the cable strands. Large and often abrupt forces are generated by the crimping tool and the cable strands are often deformed and even nicked or severed by the crimping operation. The crimping tool must be designed to prevent contact with the flat portion of the connector during the crimping operation or the large forces exerted during crimping will be transmitted to that portion and will distort the mounting hardware aperture and the flat contact surface to such an extent that the crimped connector cannot be used at the intended connection surface.
Other crimp-type connectors have been formed by crimping a portion of tube to a cable end and then shearing the mounting hardware passage through the crimped tube and cable in a single operation of the crimping tool. Shearing a cylindrical tube containing a cable causes strands to have less high-pressure contact with the entire tube interior and results in unsatisfactory electrical contact between cable and mounting surface. The force necessary to shear the tube and the cable is usually obtained from explosive expansion, requiring that a relatively complex and massive tool be used and necessitating that the tool hold both tube and cable firmly in position so as not to be prematurely ejected from the tool and thereby create a hazardous condition.
A more compact and conductive connector is formed by inserting a cable end into a sleeve having co-aligned apertures. A passage is formed by displacing the cable strands from the region defined by a line extending between the two apertures. As the cable strands are displaced and the apertures in the wall of the sleeve have been previously formed, no shearing operation is necessary. The sleeve may now be crimped to the formed cable by the application of opposed forces along the entire exterior length of the sleeve, resulting in a high conductivity electrical connection. The need for abruptly generated forces is eliminated and relatively slow and steady engagement of the crimping tool may be utilized. It is desirable that the piercing portion of the tool remain within the passage formed in the cable during the crimping operation so that the passage shape is not altered. Because of the requirement for maintaining the position of the piercing portion, the crimping tool must be constructed in such a manner that the portions of the tool exerting the crimping force are unaffected by the piercing portion, to prevent the formation of a loose contact between the connector sleeve and the cable strands in the immediate vicinity of the mounting hardware passage. This is exactly that region of the connector at which firm contact is desired so as to provide the shortest and, therefore, the lowest electrical resistance path from the cable through the connector sleeve to the terminal to which the connector is to be mounted. The proper crimping tool for a connector of this type must provide this crimping pressure in the region immediately adjacent to the aperture while forming as large a crimped surface as possible for contact with the mounting surface and also preventing the collapse or return movement of the cable strands into the mounting hardware passage.